The French government on Sunday rallied behind police in city of Marseille after three days of fan violence marred the opening days of the Euro 2016 soccer tournament and raised questions over policing tactics and security inside the stadiums.

Several hundred English and Russian fans squared off in Marseille on Saturday, hurling beer bottles and chairs and drawing volleys of tear gas from riot police who struggled to contain the skirmishes in the narrow streets of the Old Port.

Later, Russian supporters charged at their English counterparts inside Marseille's Stade Velodrome after the match, forcing panicked supporters to scale over barriers.

Then there were ugly exchanges along the Mediterranean coast between Northern Irish fans and locals in the city of Nice, where riot police again intervened.

"If there is a failure, it is that of soccer which is sick because some of its fans drink excessively and fight," Pierre-Henri Brandet, spokesman from French interior Ministry, said on BFM-TV.

Marseille's mayor said he saluted the "exemplary action of the police forces both national and local".

The Russian team could now draw sanctions from European soccer's governing body, UEFA, for crowd trouble.

As expected, UEFA said it would open an investigation, including into racist behaviour and the setting off of fireworks.

There is also likely to be public scrutiny of the reaction of stewards, who seemed caught by surprise as masked Russian fans kicked and punched retreating fans.

In Marseille, some English fans suggested the French riot police had reacted heavy-handedly and been quick to fire tear gas. Thirty-five people were hurt in the fighting, including one English fan who suffered a heart attack.

Marseille police chief Laurent Nunez told France Info radio that his force's response and prevented "much more serious damage". A total of 15 people were arrested in the city over three days.

While the tournament is being played under a state of emergency after militant Islamists attacked Paris in November, French police will be under pressure to snuff out the fan violence.

France has deployed more than 90,000 police, soldiers and private security agents across the country to ensure safety for the tournament in the face of intelligence agency warnings of potential attacks on stadiums, fan zones or other soft targets.